Pressing a piano key operates a lever attached to a felt hammer. This hammer strikes the strings and immediately recoils, allowing the strings to vibrate at their resonant frequency, producing a note. Notes are then transferred via a bridge to a soundboard, which amplifies them. Volume is controlled by depressing the keys with more or less force, making the hammer strike the strings harder or softer. The strings also have a pad (known as the damper) on them to dampen the vibrations somewhat.
Upright and grand pianos both work in exactly the same way, but on upright pianos, the mechanism is perpendicular to rather than in line with the keys.
Both types of pianos have two or more pedals. The damper (or sustain) pedal is used most often, and is placed on the right. This pedal lifts the damper pad from the strings, allowing the note to sustain for much longer than when the damper is in place. This considerably alters the piano’s tone and also allows for much smoother (legato) playing. The soft pedal (or una corda) is placed to the left of the pedal group. As its name would suggest, this softens the tone of the notes. This effect is achieved on grand pianos by shifting the keyboard slightly to the right so that the hammers only strike two of the strings rather than the usual three. On upright pianos, it is achieved by moving the hammers closer to the strings, meaning that the hammers cannot strike the strings with such force. Many pianos also have a middle pedal, known as the sostenuto pedal. This pedal allows the player to sustain some notes whilst not sustaining others by keeping raised any dampers that were in place when the pedal was pressed.
The inventor of the piano is generally credited as Bartolomeo Cristofori, an Italian instrument maker. Although he is said to have invented the instrument, Cristofori spent most of his working life building and working with harpsichords. Based on the 12-note chromatic system first seen in around 1450, the first member of the harpsichord family was the virginal. Like the harpsichord, each string on this instrument is plucked by a plectrum. This instrument was followed by the clavichord, spinnet and then the more complicated harpsichord. It was not until the year 1709 that Cristofori created the piano, which was originally essentially a modified harpsichord. Cristofori’s big breakthrough came when he invented the so-called ‘escapement mechanism’, which allows the hammers to recoil from the strings and the mechanism to reset between each key press. Although this may seem like a minor change to the basic design, the result – that the instrument is able to play at different volumes according to how hard a key is struck – has given the piano its name (pianoforte means soft and loud) and ensured its popularity as an instrument versatile enough to be used as a solo or accompaniment instrument.
This popularity was not immediate, however, and it was not really until the end of the Seven Years’ war in Germany that the instrument became genuinely popular, when twelve piano manufacturers moved to the London to begin production of the instruments for the burgeoning upper-middle classes. By 1783, the piano had begun to overtake the harpsichord in popularity, and by 1800 the first true upright piano had appeared.
Throughout the nineteenth century, composers such as Liszt and Chopin helped to further popularise the instrument by composing works that were reliant on the piano’s dynamic and expressive range. By 1850, the piano had moved from having around 4 octaves (in 1709) through 6 octaves (in the late 18th and early nineteenth centuries) to seven full octaves, with the lowest note being an A. A modified version of these instruments (with 88 keys) is what we know as the modern piano.
Throughout the latter part of the nineteenth and twentieth centuries, piano design has changed little, though perhaps the biggest leap in technology came with the development of the digital piano in the 1980s. These instruments have a completely different weighting system that imitates the weighting of a standard piano, and use digital samples to produce notes.